Inside of content, prefer SiteInstanceImpl to SiteInstance.

content/browser/frame_host/render_frame_host_impl.h

Index: content/browser/frame_host/render_frame_host_impl.h
diff --git a/content/browser/frame_host/render_frame_host_impl.h b/content/browser/frame_host/render_frame_host_impl.h
index acef076ae2f1c4b7bc2b61fd40f5fc29ce772670..9880de9c97c5d121752253a47fdc2635beefc0a0 100644
--- a/content/browser/frame_host/render_frame_host_impl.h
+++ b/content/browser/frame_host/render_frame_host_impl.h
@@ -197,7 +197,7 @@ class CONTENT_EXPORT RenderFrameHostImpl : public RenderFrameHost,
       const gfx::Rect& bounds) const override;
   gfx::Rect AccessibilityTransformToRootCoordSpace(
       const gfx::Rect& bounds) override;
-  SiteInstance* AccessibilityGetSiteInstance() override;
+  SiteInstanceImpl* AccessibilityGetSiteInstance() override;
   void AccessibilityHitTest(const gfx::Point& point) override;
   void AccessibilitySetAccessibilityFocus(int acc_obj_id) override;
   void AccessibilityFatalError() override;
@@ -383,7 +383,7 @@ class CONTENT_EXPORT RenderFrameHostImpl : public RenderFrameHost,
   // TODO(creis): Remove this method and have RenderFrameProxyHost call
   // RequestOpenURL with its FrameTreeNode.
   void OpenURL(const FrameHostMsg_OpenURL_Params& params,
-               SiteInstance* source_site_instance);
+               SiteInstanceImpl* source_site_instance);
 
   // Stop the load in progress.
   void Stop();
@@ -572,7 +572,7 @@ class CONTENT_EXPORT RenderFrameHostImpl : public RenderFrameHost,
   // TODO(nasko): Remove dependency on RenderViewHost here. RenderProcessHost
   // should be the abstraction needed here, but we need RenderViewHost to pass
   // into WebContentsObserver::FrameDetached for now.
-  RenderFrameHostImpl(SiteInstance* site_instance,
+  RenderFrameHostImpl(SiteInstanceImpl* site_instance,
                       RenderViewHostImpl* render_view_host,
                       RenderFrameHostDelegate* delegate,
                       RenderWidgetHostDelegate* rwh_delegate,